Moe divides his time between studying Physics and studying Economics. His production possibilities curve for his final grade in each class is shown below.Moe needs to earn at least an 80 in both economics and physics to keep his scholarship. Given his current PPC, an 80 in both classes is __.
A.attainable
B.inefficient
C.efficient
D.unattainable
正确答案:unattainable